Many times, after vehicle accidents, fuel is spilled. When this occurs, the spilled fuel poses a great danger of ignition, especially if power still remains in the vehicle. All it would take would be an accidental spark or contact with a charged part of the vehicle, and the spilled fuel would ignite and cause substantially more damage than an automobile accident alone would create. A number of past attempts to prevent such accidental spark from occurring are known. A number of the proposed solutions include mercury switches wherein mercury is used to form an electrical path between the switch terminals and power is interrupted or restored depending on the angle of the mercury container. It is also known to used an inertia driven sliding block to make or break the connection between terminals. See for example U.S. Pat. No. 5,602,371 issued to Kerns et al. in 1997.
U.S. Pat. No. 5,034,620, issued to Cameron, discloses an emergency cutoff switch for preventing the transmission of electrical current to a vehicle from a battery connected in an electric circuit of the vehicle.
U.S. Pat. No. 4,798,968, issued to Deem, discloses a battery disconnect apparatus for interrupting flow of power through an electrical circuit. U.S. Pat. No. 4,581,504, issued to Hamel, Sr., discloses an electrical cutoff switch in which the circuit is immediately broken by concussive distortion to the unit housing which is secured to a vehicle or aircraft powered by an internal combustion engine utilizing a storage battery as an electrical energy source.
Mercury switches are undesirable because of the danger of mercury spillage in case of an accident. In addition, modern cars have a number of electrically operated elements in addition to the ignition and lights circuits typical of older models. These elements include power locks and power windows. Cutting off all power to a vehicle as done by the type of circuit exemplified by the Kerns et al patent, while providing a measure of protection against accidental fire of spilled fuel due to an electrical spark, presents a new problem. With the windows and door lock now inoperable passengers may be trapped inside the vehicle without the ability to escape.
There is, therefore, still a need for a battery cutoff system that will disengage a vehicle battery from all but a selected number of electrical circuits in the vehicle in case of an accident.